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doc/design: fix keys.data MAC format description

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"not including the last 32 byte" was wrong, should have been 16 bytes. But the whole description is redundant anyway.
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Filippo Valsorda 2017-08-29 00:22:11 +02:00 committed by GitHub
parent 22e96a37f8
commit 3dccca1f27
1 changed files with 4 additions and 5 deletions
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doc/design.rst
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@ -315,13 +315,12 @@ divided into a 16 byte AES key ``k`` followed by 16 bytes of secret key
``r``. The key ``r`` is then masked for use with Poly1305 (see the paper
for details).
Those message authentication keys (``k`` and ``r``) are used to compute
a MAC over the bytes contained in the JSON field ``data`` (after
removing the Base64 encoding and not including the last 32 byte). If the
Those keys are used to authenticate and decrypt the bytes contained in
the JSON field ``data`` with AES-256 and Poly1305-AES as if they were
any other blob (after removing the Base64 encoding). If the
password is incorrect or the key file has been tampered with, the
computed MAC will not match the last 16 bytes of the data, and restic
exits with an error. Otherwise, the data is decrypted with the
encryption key derived from ``scrypt``. This yields a JSON document
exits with an error. Otherwise, the data yields a JSON document
which contains the master encryption and message authentication keys for
this repository (encoded in Base64). The command
``restic cat masterkey`` can be used as follows to decrypt and